Fuel burning and recuperating device



Feb. 9, 1937. F. D. HOFFMAN ,0

FUEL BURNING AND RECUPERATING DEVICE Filed Aug. 14. 1933 2 Sheets-Sheet l IN VENT OR F350 .0. 16 0 Fl w/4N I BY A Trommzs Feb. 9, 1937. F. D. HOFFMAN 2,070,536

FUEL BURNING AND RECUE ERATING DEVICE Filed Aug. 14, 1935 2 Sheets-Sheet 2 ATTORNEYS Patented Feb. 9 1937 UNITED STATES FUEL BURNING AND RECUPERATING DEVICE Fred Hoffman; Cleveland, Ohio, assignor of one-fourth to Eli E. Doster, Cleveland, Ohio Application August 14, 193 Serial No. 685,123

' 9 Claims. I (or. 110-119) This invention relates to an apparatus for effecting more eflicient combustion of carbonaceous fuel and for aerating and cleaning the products of combustion resulting from burning of such fuels.

The principal objects of the present invention are to burn carbonaceous fuels efllciently in a combustion chamberof a furnace, to aerate and eflect secondary combustion of the resultant to products and utilization of the additional heat so obtained, and to clean the products so that unburned combustible matter and soot are removed and entrapped and prevented from passing into the stack. l

Another object is to maintain a predetermined balance between the amount of air discharged through and over the fuel bed and the amount utilized for aerating and cleaning the exhaust products.

50 Still another object of the invention is to maintain automatically a balance between the rate of combustion of the fuel, the secondary combustion of the products discharged from the combustion chamber and the cleaning operation of the finally resulting products.

A correlative object is to aerate the exhaust products from the combustion chamber with air directed in a manner to effect mechanical separation of suspended matter from the products before discharge thereof into the furnace stack.

Another object is to provide a Venturi grate for discharging air over the fuel bedin the combustion chamber and to regulate the air discharged therefrom both in a predetermined relation to the air used for cleaning the products of combustion and in the predetermined relation to the heat in the combustion chamber.

Still another object is to provide a Venturi grate arranged for discharging air into the'combusv tion chamber with means in the grate for con- 5 in section for clearness in illustration;

Fig. 2 is a vertical sectional view through the I cleaning and aerating device and is taken on a plane indicated by the line 2-2 on Fig. '1;

55 Fig. 3 is a vertical sectional view through the cleaning and aerating device and is taken on the plane indicated by the line 3-4 of Fig. 2;

Fig. 4 is a cross sectional view of the cleaningand aerating device and is taken on the plane in- 60 dicated by the line 4-4 of Fig. 3.

Referring Fig. l, apreferred embodiment of f'the invention is shown, for purposes of ilustration, in conjunction with a hot air furnace'of the commonly used typecomprising a fire pot or combustion chamber C, spanned at the bottom by 5 the usual grate bars G" which admitair from the ash pit of the furnace into the combustion chamber,- the volume of air so admitted being controlled by the usual. adjustable damper D. The fire pot terminates upwardly in a radiator 10 head R" which communicates with the usual exhaust passage or flue F from which flue the products of combustion, gases and suspended matter may be exhausted from the chamber and passed to the outside atmosphere through the 15- 'furnace stack 'S.

The part of the invention most directly concemed with aerating and cleaning the products of combustion from the chamber 0 comprises a hollow body I, preferably upright and having 20 an inlet passage 2 adapted for communication with the exhaust flue F so as to receive the products discharged from the chamber 0 and discharge the same preferably horizontally transversely of the interior of the body, as indicated 25 by the arrows 3.

The body I has an exhaust passage 4 angularly disposed to the inlet passage 2 and preferably upright, the exhaust passage 4 communicating at its lower end with the interior of the body near'or 3 above the level of the inlet passage 2. A clean-out passage, closed during operation by a suitable door 5, is provided in the body wall to permit access to the interior thereof. The body is closed at the lower end by a removable hopper or bin 6 35 aligned with theexhaust passage 4.

Surmounting the body is a globular shell l0 which communicates at its lower end with the exhaustpassage 4 and is preferably coaxial therewith. At the opposite end of the shell I0 is a dis-' charge passage I l which discharges into the stack S and through this stack communicates with the outside atmosphere. Thus the exhaust gases and products issuing from the combustion chamher C pass into the body I, upwardly through the passage 4, and into the shell l0 and thence to the stack. Ordinarily, in so doing, these products would'convey suspended matter and snappreciable amount of combustible gases and heat therethrough. In order to recuperate the heat, to effect a sec ondary'combustion of the combustible gases and part of the suspendedmatter and to separate any remaining suspended matter from the products, means must be provided for passing air into the stream of products before the same pass out of the body I to aerate the same thoroughly. By the present apparatus, such air is directed-in a manner to effect also mechanical separation of 50 suspended matter from the outgoing stream of products.

For accomplishing this purpose a sleeve I2 I which forms, in effect, a continuation of the stack S; is provided, thesleeve l2 protruding inwardly of the shell Ill through the discharge passage II and extending coaxially of and part way.

through the interior of the shell Ill toward the inlet passage of the shell.

In the illustrative exampleshown, the sleeve terminates inwardly of the shell Lil beyond its mid-portion toward the inlet'passage oi the shell thus defining with the side walls ofthe shell an annular trough M. In order to introduce outside air into the shell 10 a number .of passages I 5 are provided around the periphery'of the shell, these passages being so positioned longitudinally of the shell as to discharge into the trough l4.

For controlling the volume of air admitted through the passages IS, a suitable air register l6,

preferably of the rotary type, is mounted about the circumference of'the shell Ill and cooperates with the passages l5.so'as to vary the effective size of the same as the register is rotated. Thus air entering the passage I5 through the register,

passes into the trough l4 and is heated somewhat by contact with the. sleeve l2 so that it may be mixed with the gases in the body I and ignited easily. Due to the temperature of the air being low relative to the temperature of the products" of combustion, and also due to the stack pull,

this air tends to how around the lower end'of the sleeve 12 and downwardly through the passage 4, thus forming a downwardly traveling an-' nular stream of air closely adjacent the -side walls of the. passage 4 and body I. In order toeffect better admixture of this air and products of combustion, it is desirable to maintain this stream somewhat confined and fixed in shape so that it will not readilybe destroyed'upon contact with the exhaust products entering thebody I. Furthermore it is desirable-to maintain the air as'aswirling stream so as to more effectively separate suspended 'matter from the products of-combustion coming into contact with the stream. For this purpose, a plurality of radial baflles I! are providedin the lower portion of the shell Ill extending from the side walls thereof outwardly to the sleeve l2. These baffies are curved, as illustrated in Fig. 4, for imparting a swirling motion to the air. The baiiies extend upwardly invthe trough beyond the innermostend of the sleeve l2 so that all air admitted in a direction opposite to the stream it but to' do so must pass through or into contact with this stream so as to enter and; be discharged from the passage 4. The swirling motion of the air stream imparts to the incoming products a similar swirling motion and, in turn, is heated byl the products. The resultant heated mixture, being preventedfrom rising near the side walls of the body bythe downwardly swirling air, passes toward the center of the body I and rises within the annular swirling stream, forming a funnel-shaped swirling rising stream within rection of flow. The products are thoroughly aerated during this passage and likewise are swirled with suflicient force to effect separation of any suspended matter therefrom by centrifugal I the annular stream usually tapered in the diforce. Due to the temperature of the products,

secondary'combustion is effected when they are aerated and recirculated along the comparatively long path of travel in the body I and shell Ill so as to burn any combustible gases therein and part of the suspended matter.

In order to effect more thorough aeration of the products of combustion and to direct the same more effectively into the stream IS, an opening is provided in the upper wall of the body I in a position to'admit air thereinto onto the upper surface of the incoming stream of products of combustion, this opening being controlled by a damper IS. The relatively cooler air stream,

. indicated by the arrows 20, entering this opening,

te ndsto force the incoming products downwardly, as indicated by' the arrows 3a, so that they come into contact with the stream l8 well down in the body I. The stream l8 passes rapidly downwardly toward the hopper i5 and reverses abruptly just above the hopper, when mixed with'the products and all soot thrown out of the rising stream by centrifugal force is caught in the downwardly travelling stream and thrown out of this stream as it turns to rise, thus falling into the hopper 6.

In order to vary the volume of air admitted through the passage I5, a thermostatically operable device is provided within the shell l0 so as to be more directly responsive to the temperature of the products passing through the shell and of the heat of secondary combustion. A

simple and eflective device for eflecting this operation maycomprise a horizontal rod or lever 24 fixedly secured at its ends in the rotary damper l6, suitable notches or passages 25 being provided in the walls of the shell It to permit passage 4 of the rod or lever 24 and permit a limited rotation of the lever 24 relative to the shell I0 about an upright axis. Secured to the shell I0 is a boss 26 to one end of which is fastened the end of a coil 21 of bi-metallic thermostatic metal. The thermostatic coil 21 is coaxial with the lever 24 and is secured thereto at its inner end. For. so securing the one end of the coil to the lever 24, a lug 28 is provided, the end of the thermostatic coil being secured to the-lug and the lug, in turn, being secured on the lever 24. The lug is movable to different rotated and longitudinal positions on the lever so that it may be turned or'moved longitudinally to effect predetermined torsion or stress of the bi-metallic coil 21 so that it will operate at the predetermined temperature desired. A suitable set screw 29 is provided for securing the lug 28 in the position desired. Slots 30 are formed in the lower end of the sleeve l2 to permit relative passage of the lever 24 thereacross. The thermostatic coil 21 is preferably arranged so as to rotate the damper l6 to an open position for admitting a larger quantity of air consequent upon heating of the thermostat to a higher degree of temperature-by the products and heat of secondary combustion. Thus, when the thermostat is heated, it reacts against the boss 26, and since this is fixed in position a reactionary thrust is effected on the lever 24, thus causing the lever to rotate the damper a sufficient amountto the effective size of the passages l5.

Within the combustion chamber C is a Venturi grate of the general nature disclosed in my United States Reissue Letters Patent No. 19,317, issued September 18, 1934, with certain improvements thereon to effect proper cooperation with the cleaning and aerating device above described for obtaining the desired results.

In the form illustrated the grate comprises a hollow shell body, indicated generally'as 3|, disposed in upright position in the combustion chamber C and preferably resting on the grate G". This shell is contracted from both ends toward an intermediate portion to form an upwardly contracted heating chamber 32 surmounted by an upwardly expanded expansion chamber 33 communicating at its lower end with theupper end of the heating chamber. The chambers are connected by a very short throat portion 34, the shell being open at the bottom to receive air through the grate G into the interior thereof. At the upper end of the expansion chamber is a cap 35 supported in slightly spaced relation to the upper margin of the expansion chamber so as to define therewith a peripheral discharge passage for discharging air from the interior of the Venturi grate into the combustion chamber and across the upper surface of the fuel bed.

In the side wall of the expansion chamber 33 are a plurality of discharge vents 59, the effective size of which is controlled by a register within the head 33, the register being rotatable to difierent adjusted positions by suitable levers 62.

If the damper D is *suddenly closed while only the lower strata of the fuel bed is burning at a high rate, a large amount of volatile gases is driven off from the upper strata than is consumed in the combustion chamber. These gases areaerated and burned in the body I and shell in, this secondary combustion heating the thermostatic coil in the latter and additionally opening the register Hi. This operation of the register l6 additionally checks the passage of air through the fuel bed and also, to a great extent, holds back the gases in the combustion chamber.

If the damper D is only considerably lowered, but not closed, the gases so held back eventually receive ample air through the Venturi, as little additional gas is being evolved due to the fact that the Venturi will by-pass most of the air directly into the combustion chamber under these conditions and not through the fuel bed. The gases, therefore, remain in the combustion chamber until burned. The more intense heat in the body I and shell III is reduced after most ofthe combustion of these gases in the combustion chamber is normally provided through the peripheral passage in the Venturi after the .rate of combustion for a predetermined setting of the damper D has become steady.

When'the fire is burning slowly, the vents 59 in the Venturi will be closed or only slightly vary I opened by a thermostatic register. damper contained therein and the greater portion of the air passing through the grate must discharge through the restricted peripheral passage and the side walls of the heating compartment, and

air is again drawn through the fuel bed so as to increase the rate of evolution of the gases.

.Referring again to Fig. 1, an economical and eiiicient means for controlling the various air currents and operation "of the apparatus automatically is illustrated. 'When lowering or closing the damper "D for reducing the amount of air entering the interior of the Venturi grate, the stack draft likewise should be checked and vice versa. Suddenly closing the damper fD while the under stratum is in a highly incandescent state causes evolution of an amount of combustible gases in excess of the air provided for combustion of the same. Furthermore, more air is required for aerating and cleaning this excess of gases than is supplied initially through the register I6. This additional amount is supplied through the opening controlled by the damper; l9.

For properly correlating the operation of the damper D and damper IS, a motor is provided. This motor is operably connected by a lever. mechanism 8| to the damper I9 and by a lever 82 to a suitable chain 83 operably connected to-the damper D",for lifting the same. The levers 8| and 82 are so disposed relative to each other that upon rotation of the motor in one direction they operate concurrently to close the damper l9 and to open the damper D and. upon reversal of the motor, to open the damper l9 and close the damper D. Consequently, the air introduced through the grate and that introduced into the body I are in inverse proportional relation to each other. If the damper D is fully opened, sufiicient air is normally supplied through the peripheral passage of the venturi to effect substantially complete combustion of the evolved gases while in the combustion chamber. If the heat unduly increases, the vents 59 may be opened to supply more air and also reduce the rate of evolution until a balance is again reached.

It .is apparent that when a large amount of air ismixed with the products of combustion in the combustion chamber. less is needed in the body I, and consequently these volumes of air are maintained in inverse relation to each other. To control operation of the apparatus in response to temperatures in the rooms to be heated, a thermostat is provided. The thermostat is of the double contact type, that is, one having a common movablecontacter and two stationary contacters, one of the latter being associated with the common contacter when the thermostat is cool and the other being so associated when the thermostat is heated, Separate wires lead from the stationary contacters to the device to be operated and a wire, common to the two other wires for completing circuits therewith respectively, leads to the device from the movable contacter. Thus a dual electric circuit is provided. The thermostat is connected in the dual electrical circuit in series with the motor 80 and operates when moved in one direction to close the circuit for operating the motor in one direction and when operating in the opposite direction to break the first circuit and to close the other circuit for operating the motor in the opposite direction and vice versa. The motor and thermostat circut may be connected in series to volt or other household circuit, but preferably are connected'in series with a transformer 88 which in mined degree.

turn is connected to the high voltage household circuit through the usual wall plug 81. It often happens that a particular room may require more heat than is supplied even though the furnace is operating atcapacity or at overload due to the lag in heat being conveyed from the furnace to the room. In order to protect the furnace in such instances a thermostat 88 is provided, this thermostat being normally connected in series with the thermostat 85 and the, motor 80 andclosing the circuit operable to cause the motor to open the damper I9 consequent upon heating of the thermostat 88 above a predeter- Thus the furnace and the Venturi grate are both protected from excessive temperatures. I

Assuming the apparatus to be operating with the working parts in the relative position shown in Fig. 1 only a small amount of air is introduced at the damper D". This air passes through the ash pit and grates G into the interior of the Venturi grate. At the same time, the damper I99 is open so asto check the stack pull. Conseq'uently, a comparatively small amount of air is drawn through the venturi and the stack pull is not sufficiently strong to draw any material amount of air out through the side walls of the heating compartment and through the fire bed.

Therefore slow' surface combustion 'of the fuel abundance of air over the surface for efiecting combustion of the gases and also checking the passage of air through the fuel bed so as to reduce the rate of evolution of gases. Thus a large volume of the products of combustion results and these are well mixed with air before entering the body I. These too are caught in the swirling stream within the body I and swirled rapidly so that the suspended matter is removed without requiring the addition of any large volume of air through the passage controlled by the damper I9. When very intense heat results in the body I which in turn heats the thermostatic coil 21 so that it opens the register It in the shell III, the stack pull is reduced and a large amount of air is provided in the swirling stream for aerating the products of combustion. Thus a balance in the rate of evolution of gases and the rate of combustion is maintained for all settings of the damper D.

It is apparent from the foregoing description that .the apparatus herein described operates substantially automaticallyand the working parts thereof cooperate to. produce effective combustion of the fuel and utilization of the resultant gases and un' orm fire at various temperatures and through the flue, and the soot and suspended to the reduced stack pull and then passes through the flue F" into the body I. Thoughthere may be an insufficient amount of air passing through the fuel bed and over the surface thereof with resultingimperfect combustion, since the damper I9 is open, a large quantity of air is mixed with these gases as they enter the body I thus aerating the same so that secondary combustion is effected and remaining volatile gases consumed. This heatcauses the register I6 tobe opened more widely and consequently the downwardly swirling stream is effective to swirl and aerate the incoming products-of combustion, causing any suspended matter to be thrown out so that it falls into the hopper 6 and further reducing the stack pull.

Upon additional reduction of gases passing into Therefore a larger volume of air passes through matter included in the products of combustion are entrapped in the hopper 6 and may readily be returned to the fire to be. utilized.

Having thus described my invention, I claim: 1. A device for aerating and cleaning products of combustion from a combustion chamber comprising a hollow body having an inlet passage arranged for discharging products of combustion from said chamber into the body and an exhaust passage communicating the interior of the body with the atmosphere, said passages being angularly disposed toeach other, an air vent for ad? mitting outside air into the body from a position such that it flows thereinto in a direction away from and substantially coaxially of the ucts, and means to direct said air as a swirling stream.

2. A device for aerating and cleaning products of combustion from a combustion chamber comprising a holldw' body having an inlet passage arranged for discharging said products of combustion into and across the body and an exhaust passage communicating the interior of the body with the atmosphere, said passages being angularly disposed to each other, means for admitting outside air 'into the body, so that it may flow longitudinally of the interior of the body substantially coaxially of and away from said exhaust passage, means to deflect said air spirally In those and means operable to introduce outside air into into the body so that it may flow into the interior of the body substantially coaxially of the exhaust passage and away'from said passage, means to deflect said air along a spiral path of travel, a passage for introducing outside air into the body from above downwardly onto the incoming products of combustion, and means operable'to direct said incoming products and last mentioned air toward the end of said swirling air stream remote from the exhaust passage.

4. A device for aerating and cleaning products of combustion from a combustion chamber comprising a hollow body having a substantially horizontal inlet passage arranged for passing products of combustion from a combustion chamber into the body and a substantially upright exhaust passage communicating with the interior of the body above the level of the inlet passage and with the outside atmosphere, a passage for admitting a stream of outside air into the body substantially coaxially. with the exhaust passage from a I level above the inlet passage, means to deflect said air along a spiral path of travel, means within the body arranged to deflect the incoming products of combustion downwardly and into said swirling stream, an adjustable air inlet means for discharging air in predetermined volumes into the body onto the incoming stream of products 'of combustion, and means responsive to the heat of said products of combustion operable to vary the volume of said swirling stream.

5. A device for aerating and cleaning products of combustion from a combustion chamber com-;

prising a hollow shell, an inner sleeve of smaller diameter than the shell extending thereinto from one end, an inlet passage at the opposite end of the shell aligned with said inner sleeve and'arranged to receive said products of combustion and discharge the same into the shell, the walls of said passage and inner sleeve terminating in longitudinally spaced relation to each other, said inner sleeve and shell defining a peripheral trough opening at the innermost end of the inner sleeve into the interior of the shell, air inlet means operable to introduce air into said trough, an adjustable air register associated with said air inlet means operable to vary the flow of said air therethrough, and thermostatically operable means responsive to the heat of said products of combustion to move said register to different adjusted positions. 4 a

6. A device for aerating and cleaning products of combustion comprising a hollow shell having.

the air from said trough to discharge as an annular'cyclonic stream toward and into the said incoming products.

7. A device for aerating and cleaning products of combustion from a combustion chamber comprising a hollow body, a hollow shell having an inlet passage at its iower end communicating with the upper end of the body, an inner sleeve of smaller diameter than the shell protruding thereinto from the upper end and communicating with a discharge flue, said inlet passage being aligned with said inner sleeve and arranged to receive products of combustion from said body and to discharge the same into the said shell, the walls of said inlet passage and inner sleeve terminating in longitudinally spaced relation to each other and the walls of said inner sleeve and shell defining a peripheral trough discharging around the innermost end of the inner sleeve, air inlet means for admitting air into said trough, bailles arranged near the discharge end ofsald trough operable to impart to said air a spiral swirling motion around an axis parallel to the axis of the shell, whereby a swirling annular stream coaxial with the shell nets of combustion thereinto into contact with of combustion comprising a hollow body having an inlet passage for receiving a stream of products of combustion from a combustion chamber and for discharging the same into and across the body, and an upright exhaust passage communicating with the body above the level of the inlet passage and in communication with an exhaust flue, an air inlet for admitting air into said body above the inlet passage whereby the air flows opposite to the flow of the products of combustion. means cooperable therewith to impart a swirling motionto said air and to direct said air as a swirling stream of annular cross section into contact with the products discharging into the body from said inlet passage, whereby said products are aerated and swirled and the mixture turns abruptly and rises within said annular stream and throws out suspended matter and the suspended matter passes into the outer downwardly swirling stream,

- a hopper communicating with the interior of the body below the confluence of said streams of air and products for receiving suspended matter dropping out from said swirling mixture.

9. A device for aerating and cleaning products of combustion from a combustion chamber comprising a hollow body having a substantially horizontal inlet passage for receiving products of combustion froma combustion chamber and .for discharging the same into the body and having an upright discharge passage, a globular shell surmounting said body and communicating at its lower end with the discharge passage of the body, a sleeve protruding into said globular shell from the end remote from the body and forming an exhaust passage leading from said shell and defining with the walls of said shell an annular trough, means for admitting cool outside air into said trough whereby said air may flow toward the axis of said shell and downwardly around the lower end of said sleeve, spiral baiiles cooperable with said trough to cause said air to swirl about a generally upright axis, whereby a swirling downwardly moving annular stream of air is formed extending from the lower end of said shell into the interior oi! said body, means for directing the incoming products of combustion generally downwardly and into contact with said swirling stream, an air inlet means for admitting air into said body onto the upper surface of the stream of incoming products of combustion whereby said products are aerated and caught in said swirling stream and cooled thereby and suspended matter may pass toward the'bottom of said body.

FRED D. HOFFMAN. 

